Effect of specific gravity and seed maturity on potato yields in peat soil

In a 3-year experiment in an organic soil, seed stocks of four different maturities were produced from certified Netted Gem seed. The following year, the most mature seed stock, from an early planted-late harvested crop, produced significantly lower yields than less mature seed stocks. Neither specific gravity nor size of whole seed affected the yield or specific gravity of the resulting crops.     

Influence of chemical seed and soil treatments onVerticillium-induced yield reduction and tuber defects

Experiments were conducted in 1969 and 1970 to determine the influence of chemical treatments of seed pieces and soil on the development ofVerticillium wilt as measured by tuber yield increases and reduction in severity of tuber defects. The influence of storage onVerticillium-induced tuber defects was evaluated. Seed treatment chemicals tested included zinc ion maneb, maneb, maneb-chloroneb, Polyram, benomyl, and thiabendazole. Soil treatment chemicals included O-Diethyl (O-methyl-sulfinyl) phenyl phosphoro-thioate, disulfoton, phorate, carbofuran, aldicarb, ethyl 4 (methyl- thio)-m-tolyl isopropyl phosphor amidate, benomyl, and thiabendazole. Inoculated seed pieces and artificially infested plot areas were used the first year while the second year natural inoculum from a previous crop was the source of infection. Kennebec and Katahdin cultivars were tested in 1969 and Kennebec alone in 1970. Verticillium-induced yield reductions and tuber defects were more severe in all respects with Kennebec than with Katahdin. With Katahdin the only significant evidence of infection was stem end discoloration. Seed treatments, with the exception of benomyl or thiabendazole, which were erratically phytotoxic, resulted in consistent yield increases and reduction in pink eye severity. In 1969 seed treatment reduced stem end browning in Kennebec. Soil treatment with disulfoton, carbofuran, and aldicarb, both alone and in combination with seed treatments resulted in consistent yield increases with Kennebec. The seed piece and soil treatment combinations tested in 1970 appeared to have an additive effect on yield increase from combination treatments equivalent to the gain from soil treatment alone plus seed treatment alone. The nematicide soil treatment materials did not influence yield. Tuber stem-end browning and pink eye defects in Kennebec did not increase in severity over a five month storage period.     

Relationships of seed size,spacing, stem numbers to yield of Russet Burbank potatoes

Studies were conducted in 1970 and 1971 to determine the relationships among seed size, spacing, stem numbers and yield of Russet Burbank potatoes. Cut seed sizes of 0.5, 1.0, 1.5, 2.0, 2 oz whole and a treatment consisting of 14% 0.5 oz seed, 62% 1 oz and 24% 1.5 oz seed were used in combination with seed spacings of 6, 9 and 12 inches. As seed became larger the average number of stems per seed piece increased. Percent stand and plant size rating also increased with larger seed. Total yields increased with an increase of seed size. The highest U.S. No. 1 yield was obtained with 2 oz whole seed spaced 6 inches apart with cut seed of the same size yielding slightly less. Within each spacing, the greater stem numbers per plot resulted in higher yields. However, when combinations of seed size and spacings were used to obtain a given stem number per plot, the higher stem numbers did not result in higher yields. A positive correlation coefficient of +0.982 was obtained between weight of seed piece/stem and total yield.     

Potato seed piece treatment in Washington

Although a slight amount of seed piece decay occurred, blackleg did not develop, and yield was not reduced in trials with untreated seed pieces of Norgold Russet and Russet Burbank in 1968 and 1969. Chemical seed piece treatments reduced seed piece decay, but did not increase yield. Storing untreated cut seed of these two varieties up to 5 days at 50–90 F (10–32C) and 35–86% relative humidities with adequate ventilation did not affect seed piece decay, blackleg, or yield.     

Influencing seed tuber yield of Ranger Russet and Shepody potatoes with gibberellic acid

Freshly-cut seed pieces of the potato cultivars Ranger Russet and Shepody were dipped in 0, 0.5, 1 or 2 mg/1 Gibberellic Acid (GA₃) prior to planting. GA₃ treatments increased stem and tuber numbers per hill of both cultivars and shifted tuber size profile toward the production of more seed-sized (up to 226 g) tubers and fewer large (greater than 340 g) tubers. The effect of GA₃ on reducing average tuber size was similar for the two cultivars. Total tuber yields were not affected. A 2 mg GA₃/1 seed piece dip decreased the yield of US#1 tubers in Ranger Russet primarily due to a significant increase in yield of tubers less than 226 g. Also, yields of culls were greater after a 1 mg GA₃/1 seed piece treatment, suggesting Ranger Russet is sensitive to this concentration of GA₃. One and 2 mg GA₃/1 seed piece dips to Shepody increased yields of tubers less than 113 g by 93% and reduced the yield of tubers greater than 340 g by 25% to 50%. GA₃ at 1 to 2 mg/1 may be useful in the production of seed potatoes with the cultivar Shepody which tends to produce many large tubers.     

Relation of potato compsition to potato size and blackening tendency

A compositional study was conducted on six potato samples representing various degrees of stem-end blackening. The aim of the study was to determine compositional variation with potato size. The compositional characteristics, of stem-and bud-end tissue of various potato sizes, of the six samples were determined. The larger the potato the greater was the tendency for the stem-end to have the following characteristics: (i) low citric acid content, (ii) high K/citric acid, and (iii) relatively low citric acid/polyphenolic content. It was also shown that differences in stem-end blackening tendency between potato samples, as well as differences in blackening within the same sample could be correlated with these same compositional characteristics.     

Elimination of fusarial contamination on seed potatoes

Pieces cut from seed potatoes naturally contaminated with fusarial propagules may produce poor stands if they are planted untreated in cold soils that retard sprouting. In 1972 and 1973, contaminated tubers were given various physical and fungicidal treatments in Maine to eliminate infectious propagules, and planted in North Carolina and Maine. Freshly cut and precut pieces from each of the treatments were evaluated for control of seedpiece decay. Washing tubers improved stands slightly and tended to reduce the number of small plants but did not increase yields. Precut pieces yielded significantly less than fresh cut in Maine and significantly more in North Carolina. All fungicides increased yields at both locations. Thiabendazole and benomyl practically eliminated the inoculum. In a pilot test, pieces cut from tubers sprayed with thiabendazole and benomyl in Maine produced plants and yields in North Carolina that confirmed experimental results and showed that fungicides reduce fusarial inoculum on seed potatoes.     

Effects of fungicide seed treatments on germination, population, and yield of maize grown from seed infected with fungal pathogens

Seedborne fungi can reduce survival, growth, and yield of maize (Zea mays L.). Laboratory, field, and growth chamber experiments were conducted to determine the effects of the seed treatment fungicides fludioxonil, mefenoxam, and azoxystrobin on germination, plant population, and grain yield of maize grown from low-quality hybrid seed infected with seedborne fungal pathogens. Study I used seed of four hybrids infected at 0-54% incidence with Fusarium spp., Stenocarpella maydis, Penicillium spp., Rhizopus spp., and/or Aspergillus spp. Study II used three seed lots for each of two hybrids infected at 7-37% incidence with S. maydis. Warm and cold germination for untreated seed varied among hybrids in both studies. Warm germination of the seed lot with the highest incidence of S. maydis in study II treated with azoxystrobin and fludioxonil was significantly greater (+7%) than the nontreated control. Plant population in study I was significantly affected by seed treatment, hybrid, and their interactions. Populations were greater (≥9%) for fludioxonil, fludioxonil + mefenoxam, and fludioxonil + mefenoxam + azoxystrobin treatments compared to controls. In growth chamber experiments with pasteurized soil, emergence (≥5%) and plant dry weight (≥14%) were both greater than controls only with the triple seed treatment. Plant populations in study II for all seed treatments except mefenoxam and azoxystrobin alone were greater (≥4%) than controls. Yield in study I was significantly affected by hybrid and seed treatment. Yield for one hybrid was higher (≥20%) than the control with all seed treatments except fludioxonil, whereas yield with another hybrid was consistently greater (≥26%) only with the triple seed treatment. Yield in study II was significantly affected by hybrid, seed treatment, and their interactions. Yield was greater (≥8%) than the controls for all seed treatments with one hybrid and with all (≥5%) except azoxystrobin for the other hybrid. Highest yields occurred with the triple seed treatment. Results indicate that fludioxonil and azoxystrobin can increase germination, population, and yield of maize grown from seed infected by S. maydis and other fungi.     

Effect of seed piece population on the yield and processing quality of Russet Burbank potatoes

The effect of seed piece population on tuber yield, size distribution and processing quality of Russet Burbank potatoes grown under nonirrigated conditions in southern Manitoba from 1983 to 1987 was determined. Seed pieces were planted at 21.7, 26.3, 33.3 and 45.5 thousand seed pieces per hectare, and plant emergence generally exceeded 90% of the seed piece population. Marketable tuber (greater than 5 cm in diameter) yields were not affected by seed piece population. As population increased, however, the number of harvested tubers increased and average tuber size decreased, which resulted in a decreased yield of premium tubers (greater than 284 g) and an increased yield of small tubers (less than 5.0 cm in diameter). Specific gravity, the incidence of hollow heart in maingrade (5 cm in diameter to 284 g in weight) and premium tubers, and fry color were not significantly affected by seed piece population. In the one trial tested, sucrose content decreased as population increased, however, this was not reflected in improved fry color after storage.     

Storage of seed potatoes in pallet boxes. 1. The role of tuber surface moisture on the population of Erwinia bacteria

Summary Three stocks of seed potatoes contaminated with soft rot Erwinias were stored for 172 days in a commercial pallet box store. Three treatments were applied: naturally ventilated boxes, forced air ventilated boxes and single tubers on trays. Skin resistance values were 2.3, 9.4 and 19.3 megohm respectively. Rewetting events numbered 4, 7 and 15.Erwinia carotovora pv.carotovora (Ecc) andErwinia carotovora pv.atroseptica (Eca) declined in all stocks and treatments. Ecc declined significantly faster in the forced air ventilated treatment. The more frequent rewettings in the trays reverse the benefit of their drier skins. In the earliest sprouting stock, the naturally ventilated, but not the forced ventilated boxes, showed a decrease in skin resistance and corresponding increase in Ecc as spring approached. Forced ventilation in the first 14 days after harvest halved the level of silver scurf compared to the naturally ventilated treatment.     

Erwinia species in the lenticels of certified seed potatoes

Twelve-tuber samples were collected from 39 certified seed stocks grown in 4 states and a Canadian province. One-half of each sample was immersed in water and the other half exposed to a CO₂-N atmosphere at 25C to induce soft rot development at the lenticels. Pectolytic bacteria were isolated from 24 seed stocks which represented each producing area. The pathogenicity and biochemical reactions of 20 isolates were those ofErwinia carotovora var.atroseptica, except for one isolate which grew at 37C. Four isolates did not cause black leg but only three reacted biochemically likeE. carotovora var.carotovora. The results confirm reports that theErwinia spp. are tuber borne and that anaerobic conditions stimulate infection of naturally inoculated lenticels.     

Manipulation of microtubers for direct field utilization in seed production

A two-year field study was conducted to determine the effects of jasmonic acid (JA), light (duringin vitro explant production andin vitro tuberization phases), and dormancy-breaking treatment on performance of microtubers in the production of seed tubers (pre-elite) in five potato cultivars. Microtubers were produced under short day (8-h) conditions and in darkness, from stock plantlets pre-treated with JA and untreated, and on tuberization media with or without JA. Microtuber performance was compared to invitro plantlets transplanted directly to the field. Yields of tubers from microtubers were 30% to 40% of those from plantlets. Microtubers of cultivars Amisk and Russet Burbank produced the highest yields of pre-elite tubers. Atlantic microtubers performed poorly in the field. JA pre-treatment of stock plantlets, prior toin vitro tuberization, enhanced seeds tuber production from microtubers in Russet Burbank and lowered in Shepody. JA presence in media duringin vitro tuberization significantly lowered production of tubers while exposure to 8-h light resulted in microtubers performing significantly better in the field than microtubers produced in the dark. Dormancy release was the key factor influencing microtuber performance. Unlike greenhouse studies, gibberellic acid (GA₃) was more effective than Rindite. A further refinement of the production and handling methods is required before microtubers can be recommended for field production of seed tubers.     

Potato planter performance and effects of non-uniform spacing

A survey of potato (Solanum tuberosum L.) plant stands in upstate New York over a three-year period showed that the average distance between plants was 4 cm wider than intended. Plant stands averaged 83%. The failure to plant seed pieces was the major reason for missing hills. Seed rot was not generally a problem, although one field in the survey was severely affected. Speed of planting up to 6.7 km/h had no consistent effect on average spacing or uniformity of seed piece distribution. Seed type (whole or cut) and mechanical condition of planter influenced spacing. Experiments conducted over four years indicated that the non-uniform seed piece distribution delivered by commercial picker-arm planters does not adversely affect crop yield or tuber size. Non-uniform seed distribution with extremely high coefficients of variation (greater than 100%), however, affected yield, tuber size and tuber number. Tuber numbers and yields were decreased by reducing the number of seed pieces planted per unit area whether or not the pieces were uniformly spaced.     

Establishing new guayule lines by direct seeding

Direct seeding of guayule (Parthenium argentatum Gray) in west Texas has been successful. However, studies have involved only USDA and `Mexican Bulk' lines. New selections developed by plant breeders must be screened for their adaptability to direct seeding. The objective of this study was to evaluate the standard establishment and production parameters (biomass, rubber and resin content, rubber and resin yield) of six direct seeded guayule selections (AZ-R1, AZ-R2, CAL-6, CAL-7, UC-101, and UC-104). An experiment was initiated on a Delnorte gravelly loam on 23 July 1993 at the Texas Agricultural Experiment Station near Fort Stockton, TX. Conditioned and raw seed of the six guayule selections were planted 10 mm deep on raised beds spaced 1 m apart. Laboratory seed germination ranged from 34–92%. Seedling density was greatest with conditioned seed (61 seedlings/m) versus raw seed (37 seedlings/m) when averaged across all lines 30 days after planting. Individually, seedling density in plots established by conditioned seed was greatest with CAL-6 (68 seedlings/m), UC-104 (66 seedlings/m), AZ-R1 (65 seedlings/m), UC-101 (64 seedlings/m), and CAL-7 (61 seedlings/m), and were significantly greater than the seedling density in plots established with raw seed. Both conditioned and raw seed produced adequate guayule stands. Nonetheless, conditioning improved germination, and in the field, conditioned seed was observed to germinate and emerge quicker resulting in more efficient irrigation management. The AZ-R1 seedlings were the most vigorous and were tolerant to flea beetles (Epitrix sp.). Plants were thinned to a 0.36 m spacing in April 1994. Six plants from each selection in the conditioned seed treatments were harvested on 23 February 1995 and 6 March 1996. Each plant was divided into branch (clipped 10 cm above the soil surface) and root sections. Biomass and rubber and resin yields were greatest in the branch versus root fractions. Total rubber yield (branches plus roots) at both harvests was greatest in selections AZ-R2 and UC-104.     

Verticillium albo-atrum carried by certified seed potatoes into Washington and control by chemicals

Fifty-one percent of 110 lots of certified seed potatoes from 10 states and Canada sampled in 1968 and 30% of 134 lots from nine states and Canada sampled in 1969 were infected withVerticillium albo-atrum. Fortyone percent of the 1968 lots and 13% of the 1969 lots carried soil infested with the fungus on tuber surfaces. The dark mycelial type ofV. albo-atrum was found infecting tubers more often than the microsclerotial type, however, high propapgule populations of the microsclerotial type were present on tuber surfaces in the soil of infested lots. Over 24% of the isolates ofV. albo-atrum infecting and infesting tubers from lots of seed potatoes were pathogenic to eggplant var. Black Beauty. Captan^®, household bleach (5.25% sodium hypochlorite), Polyram^®, Orthocide^®, and Semesan Bel^®, were effective in preventing germination of the fungus in small amounts of soil such as might be carried by infested tubers. Liquid treatments were more effective than dusts.     

The potential demand for seed potatoes: a world perspective

Summary For most regions of the world, estimates have been made of the quantity of certified seed potatoes available and the potential demand for them. The differences between these figures are relatively small in America and Europe, but mostly large in Africa and Asia despite marked local increases of supply since 1970. In most regions additional demands will probably be met by countries increasing their own seed production rather than by increases in imports; the latter, if any, will probably be limited to seed of newly bred high-yielding cultivars. Derived from a paper prepared for the Fourth Annual North American Seed Potato Seminar (Denver, 5–7 December 1985).     

The feasibility of predicting the number of stems per tuber produced by potato seed stocks from measurements made before planting

Summary The number of stems per seed tuber produced by 17 seed stocks of cv. Record was determined in glasshouse and field experiments to assess the feasibility of predicting the number of stems produced in the field. Multiple regression analysis showed that seed tuber weight alone gave the most satisfactory fit to stems produced in the field, which was not improved by adding terms involving the number of stems produced in the glasshouse. Quadratic relationships between the number of above-ground stems per tuber and tuber weight were most appropriate for each stock, with the fitted curves for individual stocks differing only in the constant term. However, there were significant rank correlation coefficients between the constant terms for relationships between field stems and tuber weight and glasshouse stems and tuber weight, suggesting that in other cultivars and seed stocks a predictive glasshouse test might still be useful.     

Comparison of nitrogen and phosphorus requirements between PVX free and regular Russet Burbank potato seed stocks

A Potato Virus X (PVX) free seed stock resulted in higher total yield and U.S. No. 1 potatoes than regular seed stock which carried PVX. Petiole samples from PVX free seed stock were higher in 2% acetic acid extractable PO₄-P than those from regular seed at all rates of fertilizer phosphorus. A high positive correlation was found between petiole phosphate and yield at early tuber set. Increasing rates of nitrogen increased higher total and U.S. No. 1 yields of potatoes, but also slightly decreased specific gravity. The results of this study indicate that phosphorus fertilizer recommendations for growers using Russet Burbank seed low in PVX will necessarily be different from those made for growers planting ordinary seed.     

Potato composition: III. Tissue selection and its effects on total nitrogen,free amino acid nitrogen and enzyme activity (polyphenolase,monophenolase, peroxidase and catalase)

Russet Burbank, Norchip, Kennebec, White Rose, Red La Soda and Lenape tubers were sampled at harvest, after storage for 2 and 4 mo at 7 C, and after 3 wk at 20 C following each storage treatment. Freeze-dried tissue from the bud-end, stem-end and core was analyzed for total, and free amino acid nitrogen, and for monophenolase, polyphenolase, peroxidase, and catalase activities. Significant differences among cultivars and among different parts of the tuber were found for all nitrogen fractions and all enzyme activities. Storage treatments significantly changed the total and free amino acid nitrogen contents and polyphenolase, peroxidase, and catalase activities. When compared for total nitrogen content and catalase activity, differences among different parts of the tuber which were statistically significant were similar in all cultivars. However, when compared for free amino acid content, and monophenolase, polyphenolase and peroxidase activities, differences among different parts of the tuber which were statistically significant were dependent upon which cultivar was examined. The differences among cultivars which were statistically significant for all nitrogen fractions and all enzyme activities, except peroxidase, were not significantly changed by storage treatment. The differences among different parts of the tuber which were statistically significant for quantity of both nitrogen fractions and for all enzyme activities were not significantly changed by storage.     

The influence of date of sowing and seed rate on the production of pure-sown red clover

Hungaropoly tetraploid broad red clover was sown at seed rates of 6, 12 or 18 kg ha^-1 on six dates from April to September 1971. Three crops were harvested in 1972 and one in June 1973. In 1972, total herbage dry matter yields ranged from 5.22 to 12.22 t ha^-1 and red clover dry matter yields from 3.61 to 11.92 t ha^-1 when meaned over all seed rates. April to July sowing dates gave significantly higher yields than later sowings. In general, August and September sowings gave the lowest red clover contents in a range from 63.2 to 96.5%, the highest digestibilities within a range 61.9 to 65.0% and the lowest crude protein contents in a range 15.5 to 17.3%. The influence of seed rate was less marked than sowing date. Mean annual yields of total herbage dry matter increased from 9.88 to 10.85 t ha^?1 as seed rate was increased from 6 to 18 kg ha^?1. Red clover dry matter yields and contents of red clover and crude protein in the total herbage also followed this trend. The sowing date effects on total herbage yield and content of red clover did not persist into the second harvest year but the seed rate effects were still noticeable. Plant numbers in spring the first harvest year and hence percentage survival from sowing were depressed by late sowing; plant numbers rose but percentage survival declined as seed rate was increased. The seed rate effects on plant population persisted until spring of the second harvest year but sowing date effects did not. Better stands of red clover were obtained from sowings made between April and June, when a seed rate of 12 kg ha^?1 was adequate. The adverse effects of late sowing cannot be fully compensated by raising seed rates of clover. There was a significant interaction between seed rate and date of sowing. For April-May sowings, seed rate was not critical. Thereafter, a linear effect of seed rate on yield was discernible.